Python 2 --> 3: object of type 'zip' has no len()

Question

I\'m following a tutorial on neural nets1

It\'s in Python 2.7. I\'m using 3.4. This is the line that troubles me:

if test_data: n_test = len(test_data)

Answer 1

Some Info

This is because in the Python 3.x, zip returns a generator object. This object is not a list (it's better) but it behaves like one. You can try iterating through it like this:

for i in zip([1,2,3,4], ['a','b','c','d']):
    print i

The Quick Answer

Please show us the code surrounding where the error happened. But I think I can still give you a quick (and not necessarily good) solution.

turn this

for i in reversed(range(1, len(x))):

into this:

for i in reversed(range(1, len(list(x))):